The invention relates generally to carrying straps and more particularly to cushioned straps especially suitable for use as shoulder and body straps on golf, mail, and luggage bags, back packs and baby carriers, slings for rifles and broken arms, animal collars, restraints and lifting harnesses, and a wide variety of other uses where a load is applied by a strap, surcingle or the like to a human or animal body.
Typcially, rubber or rubber-like foam material is used on or in shoulder straps and the like to spread the load and relieve pressure points on bone and tissue. While such straps are generally acceptacle, they have some disadvantages especially from the standpoint of comfort for long time wear or use. Some have a cushioned shoulder pad located along a strap at a load-bearing position but have a relatively stiff backing which presses into the user'neck, shoulder, collar bone and spine, and becomes uncomfortable with extended use; examples are the shoulder strap pads illustrated in U.S. Pat. Nos. 3,154,787 and 4,401,246; British Pat. No. 527,910; and Swiss Pat. No. 173,225. Some have a strap completely or partially in tubular form filled with cushioning material; examples are shown in U.S. Pat. No. 3,882,914, Swiss Pat. No. 63244 and French Pat. No. 1365328.
While these prior straps have user-contacting, load-bearing portions which are soft and indentible to varying extents in a transverse direction, they all have the drawback that they are inelastic lengthwise. It is my belief that lack of elasticity in this direction is an important factor in causing discomfort after extended use, as for example where a shoulder sling supports a broken arm during all a person's waking hours for several weeks or a rifle sling is supported on a soldier's or a sportsman's shoulder on a long trip. I have observed that, no matter how soft the padding is on such a strap, if the strap itself is inelastic, fatigue and discomfort results from the inability of the strap to "give" as the user's shoulder bobs up and down in a normal walking pace. This affects different people to different extents depending on the shoulder and muscle tissue development over their bones and their general physical condition, but after a while, they find it a great relief to take the loaded strap off their shoulder and allow it to rest.